In multi-hop wireless access networks, also called mesh networks, mobile nodes connect via other nodes to access points. The nodes are connected via some wireless links and reach other nodes in the mesh via some (ad-hoc) routing protocol. In addition, each node is registering via some access protocol to an access point (AP) for global connectivity. This creates a tree for each AP, where the AP (or the node directly connected to the AP) is the root. Nodes may change between APs due to mobility or other reasons, such as features of an AP or radio resource management.
FIG. 1 schematically illustrates an environment of a mesh network where there are two different access points AP1 and AP2 which may have different frequencies. One can recognize that nodes A and A′ connect to access point AP1 via node B. This means that nodes B, A, and A′ form a tree with node B being the root and nodes A and A′ being the leafs. Between the leaf nodes and the root node there may also be further intermediate nodes and further branches, however, in the example of FIG. 1 such intermediate nodes and branches are not shown for the sake of simplicity.
Assume now than terminal B wishes to change from access point AP1 to access point AP2, in other words wants to perform a “handover” from AP1 to AP2. The reason for such a handover may be the fact that B leaves the area covered by AP1 and moves to an area covered by AP2. However, there may also be other reasons due to which the handover should be performed, e.g. the need to switch to a different frequency for radio frequency management reasons, e.g., because AP1 serves much more terminals than AP2 and the radio frequency management intends to equally distribute the load in order to avoid an overload of one access point. A further reason might consist in the desire of a certain node to switch to a different service or a service of enhanced quality (e.g. a higher bitrate) which is provided by AP2 but not by AP1. Based thereupon terminal B may need to perform a handover from AP1 to AP2.
According to the prior art the node which wants to or should perform a handover has to change individually between the two access points. However, if nodes do individual handover, connectivity breaks and nodes may have to discover AP's from scratch. This would lead to service disruptions.
It is therefore desirable to perform a handover in a manner which avoids these negative effects and which increases the handover efficiency.